1. Field of Invention
The present invention relates generally to shelters and, more particularly, to shelters including collapsible frames.
2. Description of the Related Art
Over the years, a seemingly endless variety of tents and other shelters having collapsible frames have been introduced into the market. Such structures are commonly used to provide shelter during camping trips, picnics, parties, military operations and other outdoor activities. Because their frames are collapsible, relatively large shelters may be folded into a compact configuration for storage and transport.
The inventors herein have discovered that there are a number of shortcomings associated with the collapsible shelters that have been introduced heretofore. More specifically, the inventors herein have discovered that the frames associated with prior collapsible shelters tend to be difficult to fold and unfold, unstable, and somewhat large when folded. Some prior shelter frames also allow the canopy to sag and form unsightly pockets where water can accumulate, reduce tent headroom and/or ultimately produce an unsightly shelter.
For example, a prior open-type collapsible tent is shown in FIGS. 7 and 8. The tent consists of a frame which supports a canopy D. The frame includes four poles A, each of which is secured to a center strut C by a scissors-type linkage B. The scissors-type cross joints B are secured to the poles A by fixed hinges A1 at the top of each pole and sliding hinges A2 which slide along the poles as the frame is moved between the folded and unfolded orientations. The other ends of the cross joints B are secured to the center strut C by a fixed cross-shaped connector F and a sliding connector E which slides along the center strut as the frame is moved between the folded and unfolded orientations.
The shelter frame shown in FIGS. 7 and 8 is somewhat unstable because the legs A are not directly connected to one another and, instead, are only connected to one another by the structure formed by the scissors-type cross joints B, the center strut C and the connectors E and F. In addition to being unstable, the scissors-type linkage/center strut/connector structure also reduces the headroom within the tent. This frame is also somewhat difficult to unfold in that an extra person is sometimes needed to push the center strut C upwardly to its completely extended position. With respect to the canopy D, the center strut C is the only portion of the frame that holds the canopy above the poles and, as a result, the canopy will often sag.
Another example of a conventional shelter frame is shown in U.S. Pat. No. 4,607,656 (“the '656 patent”) the contents of which are hereby incorporated by reference. The frame disclosed in the '656 patent is a marginal improvement over the frame illustrated in FIGS. 7 and 8 in that stability is increased because adjacent support poles are connected to one another by respective pairs of scissors-type cross joints. Nevertheless, the shelter frame disclosed in the '656 patent suffers from many of the same shortcomings as the frame shown in FIGS. 7 and 8. For example, the canopy is supported by a single central support and, therefore, tends to sag. The central support post is itself supported by a pair of scissors-type cross joints which extend across the interior of the shelter. This configuration reduces headroom within the shelter. Moreover, the lowest portion of each of the scissors-type linkage pairs is half way between the poles, thereby reducing headroom in the area that often serves as the entrance to a tent.
Another example of a shelter frame is shown in U.S. Pat. No. 6,035,877 (“the '877 patent”) the contents of which are hereby incorporated by reference. The frame of the '877 patent represents an improvement over previous designs by providing a modified canopy frame design that eliminates a central support member, providing additional usable room beneath the portable shelter.
Despite these improvements, shelter frame designs remain difficult to expand and contract, especially for a single user. Nearly all previous shelter frame joints use a single bolt to fasten multiple members together while attempting to allow for rotational movement relative to each other. This arrangement creates friction between members which in turn makes expansion or contraction of the joint more difficult. Consequently, portable shelter manufacturers are caught between two equally undesirable alternatives: tighten the bolts of these joints very tightly or leave the bolts relatively loose. If the joint bolts are significantly tightened, the shelter frame will be more structurally secure at the cost of considerable increased friction. On the other hand, leaving the bolts relatively loose reduces the above mentioned joint friction but increases the “play” in the joints, greatly reducing shelter frame structural integrity, increasing joint wear, and decreasing the lifespan of the shelter.
What is needed is an improved shelter frame design that provides maximum usable room within the shelter, structural integrity, and minimal force to expand or contract.